diff --git a/Headers/Foundation/NSThread.h b/Headers/Foundation/NSThread.h
index 037a04331..ca5c76291 100644
--- a/Headers/Foundation/NSThread.h
+++ b/Headers/Foundation/NSThread.h
@@ -52,6 +52,7 @@ extern "C" {
   NSMutableDictionary	*_thread_dictionary;
   struct autorelease_thread_vars _autorelease_vars;
   id			_gcontext;
+  void                  *_runLoopInfo;  // Per-thread runloop related info.
   void                  *_reserved;     // For future expansion
 }